Chapter 85: The Antiphospholipid Syndrome

INTRODUCTION

• The antiphospholipid syndrome is an acquired thrombotic disorder associated with circulating autoantibodies to anionic phospholipid–protein complexes.

• These antibodies were first detected as inhibitors of the activated partial thromboplastin time (aPTT) in patients with systemic lupus erythematosus (SLE) and, for this reason, were called “lupus anticoagulant,” although this finding is not limited to patients with lupus, nor is the clinical syndrome that of bleeding.

PATHOGENESIS

• The disorder is generally considered to be autoimmune, although a direct causal relationship between antiphospholipid antibodies and thrombosis or pregnancy problems has not been demonstrated.

• The antiphospholipid antibodies found in the syndrome usually react with phospholipid bound to a plasma protein.

• A number of pathogenetic mechanisms have been proposed for the antiphospholipid syndrome, and it is possible that several of these act in concert to cause the disorder.

CLINICAL FEATURES

• Patients usually present with manifestations of thrombosis and/or pregnancy complications or loss.

• The disease usually presents in patients between ages 35 and 45 years. Both sexes are equally susceptible.

• The disorder is considered “secondary antiphospholipid syndrome” if the patient has a recognizable autoimmune disease or “primary antiphospholipid syndrome” if there is no associated disorder.

• Table 85–1 summarizes the clinical manifestations of the antiphospholipid syndrome.

• The antiphospholipid syndrome should be considered in patients with recurrent thromboses in unusual locations.

• Venous and/or arterial thromboses may occur at any site but are most frequent in the lower extremities.

• Patients with concurrent inherited thrombophilia (eg, factor V Leiden) who develop antiphospholipid antibodies are at increased risk for thrombosis.

• Immune thrombocytopenia, usually of mild to moderate severity, occurs frequently in patients with antiphospholipid syndrome.

• Rarely, patients may develop a catastrophic form of the antiphospholipid syndrome, with severe, widespread vascular occlusions, despite intense anticoagulant treatment, often leading to death.

• Recurrent pregnancy loss occurs often in women with the antiphospholipid syndrome. About one-half of the spontaneous abortions occur after the first trimester.

• Some patients develop a bleeding disorder because of a concurrent coagulopathy, such as acquired hypoprothrombinemia, or because of acquired inhibitors of factor VIII (see Chap. 83).